How come the older I get the more I want to believe the Patterson-Gimlin film is real despite knowing it's been a obvious hoax since day 1?

Only you can really answer that question, but here's my take at least.

When we are young, the world feels magical and mysterious. We are convinced that there's dragons living in the mountains, and kraken in the oceans. We are so sure that we spotted a fairy in the garden or a mermaid at the pool And then there's the Easter Bunny and Santa Clause who leave an obvious trace. But as we get older, that magic seems to fade. We instead see the world for the boring corporate reality that it is. And yet there's still a part of us that hopes. Hopes that Bigfoot is walking around out there somewhere. Hope that Nessy really is swimming around in some undiscovered cave network beneath Scotland. Hope that the fuzzy photo of a smudge really is an Alian spacecraft come to make our world feel magical again.

As the great Sir Terry Pratchet once wrote

“All right," said Susan. "I'm not stupid. You're saying humans need... fantasies to make life bearable."

REALLY? AS IF IT WAS SOME KIND OF PINK PILL? NO. HUMANS NEED FANTASY TO BE HUMAN. TO BE THE PLACE WHERE THE FALLING ANGEL MEETS THE RISING APE.

"Tooth fairies? Hogfathers? Little—"

YES. AS PRACTICE. YOU HAVE TO START OUT LEARNING TO BELIEVE THE LITTLE LIES.

"So we can believe the big ones?"

YES. JUSTICE. MERCY. DUTY. THAT SORT OF THING.